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The adsorption mechanism of Cd (II) was investigated by Pennisetum sp. straw biochars (JBC) that were modified by two different methods: KMnO4 impregnation (JMB1) and H2O2 impregnation (JMB2). A scanning electron microscope and energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), a Fourier transform infrared spectrometer (FTIR), and a Brunauer-Emmett-Teller (BET) specific surface area analysis were employed to examine the physicochemical characteristics of biochars. The Cd(II) adsorption kinetic fit, the Langmuir model well, and the maximum adsorption capacity occurred in the following order: JMB1 (90.32 mg/g) > JMB2 (45.18 mg/g) > JBC (41.79 mg/g), suggesting that JMB1 had an excellent adsorption performance. Finally, X-ray photoelectron spectroscopy (XPS) was used to explore the main adsorption mechanism. Our results showed that JMB1 was an excellent adsorbent in removing Cd(II) from aqueous solution.
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